About 200 species, 100 trillion (1014) or more intestinal bacteria (intestine-colonizing microorganisms) inhabit the human intestine. Microorganisms called probiotics improve the intestinal balance between useful and harmful bacteria, contributing to host health. Recently, a trend is to apply these probiotic microorganisms to foods. For example, several kinds of functional yogurt produced using lactobacilli with probiotic functions have been commercialized. Thus, a mass screening technique for selecting more excellent probiotics is required.
Intestine-colonizing lactobacilli propagate while adhering to the human intestine. Thus, the property of lactobacilli to bind to the intestine is very important for the exertion of probiotic functions. The binding mechanism of lactobacilli in the human intestine is not yet elucidated. Prior studies on intestinal lactobacilli have confirmed that Lactobacillus casei has the ability to bind to sugar chains of glycolipids and that L. reuteri and L. crispatus have a collagen-binding ability. In addition, lectin-like proteins which bind to the above-mentioned intestinal lactobacilli have been identified. However, cytoskeleton protein (collagen)-exposed areas are very few in the intestinal epithelia of most healthy individuals, and colonization of lactobacilli via lectin-like proteins in the intestinal epithelia is unlikely. Thus, sugar chains that bind to intestinal mucin are considered to play an important role in ability of intestine-colonizing lactobacilli to bind to the intestine. Surface layer proteins (SLPs) of many intestine-colonizing lactobacilli have lectin-like proteins, which are sugar-recognizing proteins. Intestinal mucin exists on intestinal surface.
Intestinal mucin is a mucous high-molecular-weight glycoprotein having countless mucin-type sugar chains linked to a polypeptide (a core protein, apomucin) via O-glycosidic linkages. In sum, intestine-colonizing lactobacilli are considered to acquire intestine-binding ability by binding to sugar chains of intestinal mucin through lectin-like proteins on their surface and establishing a stable growth.
Meanwhile, an interesting fact that has recently been reported is that the chemical structure of sugar chains constituting human colonic mucin (HCM) varies depending on the ABO blood group (Non-Patent Documents 1 to 4).
Human ABO blood groups are distinguished depending on the type of antigenic substance expressed on red blood cell surface. The antigenic sites of these ABO blood group substances are sugar chains of certain chemical structures (ABO blood group antigens). Both blood group A- and B-antigens are molecules consisting of three sugars. The blood group A-antigen is a molecule in which an α-N-acetylgalactosamine is bound to a basic structure called blood group H antigen that consists of two sugars through a specific linkage mode, whereas the blood group B antigen is a molecule in which α-galactose is bound. Humans of blood group A, blood group B, and blood group AB express A antigen, B antigen, and both A and B antigens on the surface of red blood cells, respectively. In contrast, humans of blood group O express H antigen, which is the basic structure.
The above scientific fact that the sugar chain structure of digestive-tract mucin varies blood group-dependently suggests that the type of probiotic lactobacilli that bind to and grow in the digestive tract varies depending on the blood group. Development of functional yogurt tailored at individual levels will be made possible if lactobacilli that are compatible with each blood group are found. Focusing on this point, the present inventors have hitherto developed a method of screening for human intestine-binding lactobacilli using their adsorbability to ABO blood group antigens (Patent Document 1). This is an epoch-making method that detects adsorbability of lactobacilli to ABO blood group antigens by using surface plasmon resonance (SPR) spectrums, and thereby selecting compatible lactobacilli according to blood groups. Specifically, by using ABO blood group antigens or intestine-derived mucin as ligands, the method detects the binding between lactobacilli and the ligands occurring when the lactobacilli are contacted with the ligands immobilized on a sensor chip, through detecting a mass change on the sensor chip which accompanies the binding as a surface plasmon resonance (SPR) signal. The above-mentioned mass change is expressed by resonance units (RU). One RU equals 1 pg/mm2, and means that 1 pg of a substance is bound per 1 mm2. The present inventors carried out the above method, and confirmed that Lactobacillus crispatus JCM8778 strain and Lactobacillus acidophilus OLL2769 strain recognize blood group A antigen (Patent Document 1 and Non-Patent Document 5). However, an increased demand for foods that use probiotic lactobacilli including yogurt is expected, and thus acquisition of lactobacilli having blood group specific binding capabilities and with better binding properties has been awaited.    [Patent Document 1] Japanese Laid Open Patent Application No. 2004-101249 (unexamined, published Japanese patent application)    [Non-Patent Document 1] Junko Amano, Seikagaku, The Japanese Biochemical Society, 1999, Vol. 71, p. 274-277    [Non-Patent Document 2] Holgersson, J., Stromberg, N., and Breimer, M. E., Glycolipids of human large intestine: glycolopid expression related to anatomical localization, epithelial/non-epithelial tissue and the ABO, Le and Se phenotypes of the donors. Biochimie, 70, 1565-1574 (1988).    [Non-Patent Document 3] Holgersson, J., Jovall, P. A., and Breimer, M. E., Glycosphingolipids of human large intestine: detailed structural characterization with special reference to blood group compounds and bacterial receptor structures. J. Biochem, (Tokyo), 110, 120-131 (1991).    [Non-Patent Document 4] Vanak, J., Ehrmann, J., Drimalova, D., Nemec, M., monoclonal antibodies in the detection of blood group antigens A and B in the mucosa of the large intestine. Cas Lek Cesk, 18, 364-367 (1988).    [Non-Patent Document 5] Uchida, H. et al., Biosci. Biotechnol. Biochem., 68(5), 1004-1010 (2004).    [Non-Patent Document 6] Holmes, S. D. et al., Studies on the interaction of Staphylococcus aureus and Staphylococcus epidermidis with fibronectin using surface plasmon resonance (BIACORE)., J. Microbiological Methods, 28, 77-84 (1997).    [Non-Patent Document 7] Fratamico, P. M. et al., Detection of Escherichia coli O157:H7 using a surface plasmon resonance biosensor. Biotechnol. Techniques. 7, 571-576 (1998).